The interconnection part of an integrated circuit comprises in a conventional manner at least one metallization level, and in general several metallization levels each comprising electrically conducting lines, for example metallic lines such as copper lines, making it possible to interconnect the various components of the integrated circuit to one another and/or to the inputs-outputs of the integrated circuit.
In order to supplement this interconnection, the interconnection part also generally comprises one or more levels of vias, according to a terminology commonly used by the person skilled in the art, situated between the metallization levels and making it possible to link together certain metallic lines.
In certain cases, premature breakdown of an interline dielectric region separating two metallic lines may occur, in particular when these two lines are separated by a very small distance, for example equal to the minimum distance specified by the CMOS technological node used.
This is all the more critical as the CMOS technological node gets ever more advanced, that is to say when this minimum distance becomes ever smaller.
It was indicated in the French Application for Patent No. 1559337 (U.S. patent application Ser. No. 15/137,063, incorporated by reference) that this phenomenon of premature breakdown occurred in particular in the presence of a potential difference applied between the two metallic lines, combined with ingress of moisture and/or ionic contamination into the dielectric in particular when the latter is porous.
It has consequently been deduced therefrom that this phenomenon of premature breakdown was due to a conduction mechanism assisted by the presence of defects (traps) in the dielectric. More precisely, the electrons then propagate by jumps between states located in the forbidden band of the dielectric which are assumed to be ionized centers (donors of electrons). This effect results from the lowering of the energy of ionization of these centers with the application of an electric field (potential difference between the lines). This conduction mechanism is then manifested by a current dubbed the Poole-Frenkel current after the name of the two people who demonstrated in a general manner such a mechanism within a dielectric.
In the aforementioned French patent application, it was proposed to afford a solution to this premature dielectric breakdown through the use of at least one non-porous dielectric barrier inserted between a porous part of at least one dielectric region and at least one of two electrically conducting elements, for example a metallic track or line or a via, of an interconnection part of an integrated circuit, so as to protect this integrated circuit against a breakdown of the at least one dielectric region caused by electrical conduction assisted by the presence of defects within the at least one dielectric region.
Stated otherwise this solution is aimed at rupturing as far as possible the conduction path liable to exist more or less long-term in the dielectric, that is to say prevent as far as possible the flow of a leakage current of Poole Frenkel type between the two electrically conducting elements separated by this dielectric region, by using at least one non-porous dielectric barrier.
This being so, it is observed that certain situations were favorable to the appearance of moisture in the porous dielectric regions of the interconnection part. Such is the case in particular when the integrated circuit is situated within a continually powered apparatus, such as for example a TV decoder, the temperature of the integrated circuit then possibly nearing 60-70 degrees Celsius.
Now, as indicated hereinabove, this moisture may lead to the creation of a conduction path in a porous dielectric.
Even if the solution described in the aforementioned French patent application is satisfactory, a need exists to reduce as far as possible, or indeed eliminate, this appearance of moisture within the regions of porous dielectric of an integrated circuit, and this will consequently reduce the risk of premature dielectric breakdown.